To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Device to Device (D2D) communication is being studied in communication standard groups to enable discovery and data communication services between one or more devices. Discovery is a process which determines that a D2D-enabled User Equipment (UE) is in proximity of another D2D-enabled UE. A discovering D2D-enabled UE determines whether or not another D2D-enabled UE is of interest to the discovering D2D-enabled UE using D2D Discovery. The D2D-enabled UE is of interest to a discovering D2D-enabled UE if proximity of D2D-enabled UE needs to be known by one or more authorized applications on the discovering D2D-enabled UE. For e.g. a social networking application can be enabled to use D2D discovery feature. The D2D discovery enables the D2D-enabled UE of a given user of a social networking application to discover and be discoverable by the D2D-enabled UEs of his/her friends. In another example, the D2D discovery can enable the D2D-enabled UE of a given user of a search application to discover stores/restaurants etc. of its interest in its proximity. In another example, the D2D-enabled public safety UE would need to discover other D2D-enabled public safety UE, which belong to the same group, is in its proximity. Also, a D2D-enabled UE may need to discover whether any group members are in its proximity. Further, the D2D-enabled UE discovers other D2D-enabled UEs in its proximity by using direct UE-to-UE signaling.
According to the existing discovery mechanism, the discovery message transmitted for discovery comprises of discovery information (discovery code), Message Integrity Code (MIC) and 4 least significant bits (LSBs) of time counter. The discovery code is a pseudo ID assigned to each user of a discovery application in the UE. In order to protect the discovery information against replay and impersonation attack a security key is assigned to each discovery code by a ProSe Function and provided to the UE. The discovery message is protected as shown in FIG. 1. A transmitter of discovery message secures the discovery message using the security key corresponding to the discovery code in the discovery information being transmitted. The time stamp (or time counter) corresponding to the discovery slot in which the discovery information is transmitted is also used as an input to security algorithm. The receiver of discovery message sends the received discovery information together with MIC and time stamp (or time counter) corresponding to discovery slot in which discovery message is received to the ProSe function. The ProSe function validates the MIC using the security key corresponding to the discovery code.
Currently, it is being discussed to use the discovery mechanism for public safety communication to discover group members. Each public safety UE belongs to one or more groups. FIG. 2A illustrates an exemplary discovery mechanism used to discover a group member. As shown in FIG. 2A, a discoverable UE (also known as announcing UE) periodically announces a discovery message. A discovering UE which wants to discover another member of its group periodically monitor discovery channel for discovery message announced by the member being discovered.
FIG. 2B illustrates another exemplary discovery mechanism used to discover a group member. As shown in FIG. 2B, a discoverer UE which wants to discover another member of its group transmits a discovery message 1, indicating that it is searching for a specific member of its group. The discoverer UE monitors the discovery channel for a discovery message from discoveree UE after sending the discovery message 1. The discoveree UE (i.e. UE being discovered) monitors the discovery channel for discovery message 1 indicating that a discoverer UE is searching for it. If the discoveree UE receives a discovery message 1 searching for it from a discoverer UE then the discoveree UE announces a discovery message 2 with its information.